nr,gnb,rrc: restore the GTPU TEIDs back from NR RNTI to LTE RNTI when RRC reconfiguration fails

srsenb/hdr/stack/rrc/rrc_endc.h

@@ -36,8 +36,9 @@ public:
   struct sgnb_add_req_ack_ev {
     sgnb_addition_ack_params_t params;
   };
-
   struct sgnb_add_req_reject_ev {};
+  /// Called when Reconf fails
+  struct rrc_reest_rx_ev {};
 
   /**
    * @brief Non-standard event sent from NR-RRC to EUTRA when UE has attached to NR cell
@@ -98,6 +99,7 @@ private:
 
   // FSM transition handlers
   void handle_sgnb_add_req_ack(wait_sgnb_add_req_resp_st& s, const sgnb_add_req_ack_ev& ev);
+  void handle_rrc_reest(wait_add_complete_st& s, const rrc_reest_rx_ev& ev);
 
 protected:
   // states
@@ -120,7 +122,8 @@ protected:
   row< wait_sgnb_add_req_resp_st, prepare_recfg_st,          sgnb_add_req_ack_ev,     &fsm::handle_sgnb_add_req_ack                         >,
   row< wait_sgnb_add_req_resp_st, endc_deactivated_st,       sgnb_add_req_reject_ev                                                         >,
   row< prepare_recfg_st,          wait_add_complete_st,      rrc_recfg_sent_ev                                                              >,
-  row< wait_add_complete_st,      endc_activated_st,         sgnb_add_complete_ev                                                           >
+  row< wait_add_complete_st,      endc_activated_st,         sgnb_add_complete_ev                                                           >,
+  row< wait_add_complete_st,      endc_deactivated_st,       rrc_reest_rx_ev,         &fsm::handle_rrc_reest                                >
   // +---------------------------+--------------------------+------------------------+------------------------------+-------------------------+
   >;
   // clang-format on

srsenb/src/stack/rrc/rrc_endc.cc

@@ -168,7 +168,7 @@ bool rrc::ue::rrc_endc::fill_conn_recfg(asn1::rrc::rrc_conn_recfg_r8_ies_s* conn
         .non_crit_ext_present                = true;
     rrc_conn_recfg_v1510_ies_s& reconf_v1510 = conn_recfg->non_crit_ext.non_crit_ext.non_crit_ext.non_crit_ext
                                                    .non_crit_ext.non_crit_ext.non_crit_ext.non_crit_ext;
-    reconf_v1510.nr_cfg_r15_present     = true;
+    reconf_v1510.nr_cfg_r15_present = true;
     reconf_v1510.nr_cfg_r15.set_setup();
 
     reconf_v1510.nr_cfg_r15.setup().endc_release_and_add_r15                = false;
@@ -319,4 +319,14 @@ bool rrc::ue::rrc_endc::is_endc_supported()
   return endc_supported;
 }
 
+void rrc::ue::rrc_endc::handle_rrc_reest(wait_add_complete_st& s, const rrc_reest_rx_ev& ev)
+{
+  auto& sgnb_config = get_state<prepare_recfg_st>()->sgnb_config;
+
+  // Transition GTPU tunnel rnti back from NR RNTI to LTE RNTI, given that the reconfiguration failed
+  rrc_enb->gtpu->mod_bearer_rnti(sgnb_config.nr_rnti, rrc_ue->rnti);
+
+  rrc_enb->bearer_manager.rem_user(sgnb_config.nr_rnti);
+}
+
 } // namespace srsenb

srsenb/src/stack/rrc/rrc_ue.cc

@@ -652,6 +652,10 @@ void rrc::ue::handle_rrc_con_reest_req(rrc_conn_reest_request_s* msg)
   srsran::console(
       "User 0x%x requesting RRC Reestablishment as 0x%x. Cause: %s\n", rnti, old_rnti, req_r8.reest_cause.to_string());
 
+  if (endc_handler != nullptr) {
+    old_ue->endc_handler->trigger(rrc_endc::rrc_reest_rx_ev{});
+  }
+
   // Cancel Handover in Target eNB if on-going
   asn1::s1ap::cause_c cause;
   cause.set_radio_network().value = asn1::s1ap::cause_radio_network_opts::interaction_with_other_proc;

srsenb/src/stack/upper/gtpu.cc

@@ -124,14 +124,16 @@ gtpu_tunnel_manager::add_tunnel(uint16_t rnti, uint32_t eps_bearer_id, uint32_t
 bool gtpu_tunnel_manager::update_rnti(uint16_t old_rnti, uint16_t new_rnti)
 {
   auto* old_rnti_ptr = find_rnti_tunnels(old_rnti);
-  if (old_rnti_ptr == nullptr or find_rnti_tunnels(new_rnti) != nullptr) {
+  auto* new_rnti_ptr = find_rnti_tunnels(new_rnti);
+  if (old_rnti_ptr == nullptr or (new_rnti_ptr != nullptr and not new_rnti_ptr->empty())) {
+    // The old rnti must exist and the new rnti TEID list must be empty
     logger.error("Modifying bearer rnti. Old rnti=0x%x, new rnti=0x%x", old_rnti, new_rnti);
     return false;
   }
   logger.info("Modifying bearer rnti. Old rnti: 0x%x, new rnti: 0x%x", old_rnti, new_rnti);
 
   // create new RNTI and update TEIDs of old rnti to reflect new rnti
-  if (not ue_teidin_db.insert(new_rnti, ue_bearer_tunnel_list())) {
+  if (new_rnti_ptr == nullptr and not ue_teidin_db.insert(new_rnti, ue_bearer_tunnel_list())) {
     logger.error("Failure to create new rnti=0x%x", new_rnti);
     return false;
   }